cortical control of the eye movement is exerted by what fibers from the cortex? These fibers then project to where?

corticobulbar fibers; to brainstem centers, particularly the superior colliculi and the gaze centers (areas of reticular formation that program eye movement)

what gaze center moves both eyes to the same side at the same time? what is the path of its fibers?

the lateral gaze centers AKA PPRF or abducens; it is found in the brainstem RF at the level of the facial colliculus (the pons) and it sends fibers to the ipsilateral abducens nucleus and contralateral occulomotor nucleus (via the medial longitudinal fasciculus for occulomotr nucleus). Note that antagonistic muscles are inhibited and there are two centers (a left and right) and the left one moves both eyes to the left and vice versa

This brainstem nucleus moves the eyeballs conjugately up or down involving synchronus excitation or inhibition of four muscles... where is it located? what parts does it consist of? what cranial nerve nuclei does it project to ?

the vertical gaze center AKA rostral interstitial nucleus of the MLF. found at the level of the superior colliculus (midbrain), consists of upward and downward parts, and projects to the occulomotor and trochlear nuclei

this nucleus directs convergence and divergence eye movements... what complex is it apart of? what is different about its tract compared to the other gaze centers' tracts?

perlia's nucleus AKA supraoculomotor area. the occulomotor complex, its fibers do not use the MLF

the brainstem centers for eye movement control two types of cells. What are they and what do they do?

this nucleus is believed to integrate signals for saccadic movements to derive a new position signal that is sent to tonic cells.

nucleus prepositus hypoglossi

an occulomotor channel through the basal ganglia does what to eye movements? what is an example of one of these channels? the effect of the example is greatly enhanced in what condition?

suppresses or facilitates them; GABA neurons in the substantia nigra, pars reticulara that usually exert a tonic inhibitory effect on eye movements ceases fire during saccadic movement. Oculogyric crisis where the eyes are fixed upwards for long times is seen in parkinsonism from encephalitis

this part of the cortex is located in the middle frontal gyri and receives input from the visual cortex to direct voluntary rotation of both eyes... where do its fibers project?

frontal eye fields; fibers to the vertical and contralateral gaze centers and the ipsilateral superior colliculus

where is the visual association cortex located? what does it control? where do its fibers project too?

surrounds the primary visual cortex in the occipital lobe and includes parietal and temporal areas. it directs smooth pursuit
(tracking) movements mainly to the same side. to the lateral and vertical gaze centers and the superior colliculi.

conjugate eye movements involve what? vergent?

both eyes move in same direction; each eye moves in different direction

voluntary eye movements are classified as what? controlled by what? propagated by what cells? and the final position is held in place by what cells?

saccadic; frontal eye fields; burst cells; tonic cells

while saccadic movement occurs, the frontal eye fields receive input from the visual cortex. What can they do with this input?

they can utilize it or disregard it

the cortical reflex circuit does what? what areas of the brain does it use?

tracking a moving object by having the eyes lock onto that moving object. Uses the visual association cortex, parietal and temporal areas all integrated with the vestibular and flocculonodular signals.

the vestibulo-ocular reflex results from the stimulation of what causing the eyes to do what? what is this reflex used for clinically?

endolymph in the semicircular canals moves when the head is turned, causing the eyes to move in the opposite direction of the head rotation, this enables the eyes to remain fixed on a stationary object. used to evaluate brainstem injury in the unconscious patient

what is the optokinetic reflex? failure to elicit this reflex means what?

normal reflex induced by movement of the whole visual field across the retina AKA retinal slip. cortical lesion since it involves areas 18, 19 and the visual parietal and temporal areas

visual, auditory, and somatosensory reflexes are elicited subcortically via tracts to what? In terms of visual sensation, what is significant about this area?

the superior colliculi which have a retinotopic organization (contralateral) causing movement of the retina to that part stimulated.

the accomodation-convergence reflex is used for what? what are its three aspects?

for near vision; convergence (eyes rotate medially), accommodation (focus for near vision), and miosis (pupil becomes smaller to increase depth of focus)

misalignment of the two eyeballs resulting in fatigue of the extraocular eye muscles. This results in cortical suppresion of the image of the defective eye and subsequent loss of visual acuity (amblyopia). This is permanent in aninfnt if it is not corrected within about six months.